The vacuum ultraviolet fluorescence from the atomic photofragments of O2and N2produced by extreme ultraviolet excitation has been investigated and their production cross sections measured. The processes were studied using synchroton radiation, in the lgr;lgr;175ndash;780 Aring; region, to excite the gases. The nature of the fluorescence spectrum in the wavelength range lgr;lgr;1050ndash;1800 Aring; was studied by using a combination of optical and gaseous filters. The dependence of the intensity of the fluorescence radiation on the gas pressure was studied in order to determine the relative contributions from direct excitation and photoelectron excited emissions. Direct excitation processes were verified to be the primary contributor, particularly at low pressures. In the incident wavelength range lgr;lgr;200ndash;350 Aring;, the cross sections for the production of fluorescence for each gas shows a broad band, which is presumably produced by dissociative ionization processes. In the longer wavelength region, discrete structure was observed at the positions of known Rydberg series. These features are the result of the interaction of dissociation continuum states with bound states. Photodissociation continua were also observed in the lgr;lgr;400ndash;780 Aring; region.
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